# Module Federation

Module Federation is an architectural pattern for JavaScript application decomposition (similar to microservices on the server-side), allowing you to share code and resources between multiple JavaScript applications (or micro-frontends).

The Rspack team works closely with the Module Federation development team and provides first-class support for Module Federation.

## Use Cases

Module Federation has several typical use cases, including:

- Allowing independent applications (called "micro-frontends" in micro-frontend architecture) to share modules without recompiling the entire application.
- Different teams working on different parts of the same application without needing to recompile the entire application.
- Dynamic code loading and sharing between applications at runtime.

Module Federation can help you:

- Reduce code duplication
- Improve code maintainability
- Reduce the overall size of applications
- Improve application performance

## How to use

Module Federation (MF) currently has multiple major versions, and you can choose one based on your needs.

Here are the characteristics of several versions:

| Version | Description                                                                        | Features                                                                                                                                                                                                                                                                  | Use Cases                                                        |
| ------- | ---------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------- |
| MF v2.0 | Enhanced version of Module Federation, implemented based on Module Federation v1.5 | - Provides additional out-of-the-box features such as dynamic TS type hints, Chrome DevTools, preloading, etc.<br />- More suitable for micro-frontend architecture supporting large-scale Web applications <br />- Includes all features of Module Federation 1.5 <br /> | Projects that need to use advanced capabilities of MF 2.0        |
| MF v1.5 | Version built into Rspack                                                          | - Supports module export, module loading, dependency sharing capabilities of Module Federation v1.0<br />- Added runtime plugin functionality, allowing users to extend the behavior and functionality of module federation <br />                                        | Projects that don't need to use the extra capabilities of MF 2.0 |

### Module Federation v2.0

[Module Federation 2.0](https://module-federation.io/blog/announcement.html) provides some additional out-of-the-box features based on Module Federation, such as dynamic TS type hints, Chrome devtools, Runtime plugins, preloading, making Module Federation more suitable for micro-frontend architecture supporting large-scale Web applications. Module Federation v2.0 is implemented based on v1.5.

You need to install the additional [@module-federation/rsbuild-plugin](https://www.npmjs.com/package/@module-federation/rsbuild-plugin) plugin to use Module Federation v2.0.

```ts title="rsbuild.config.ts"
import { pluginModuleFederation } from '@module-federation/rsbuild-plugin';

export default defineConfig({
  plugins: {
    pluginModuleFederation({
      name: 'remote',
     // other options
    }),
  },
});
```

Please refer to the [Module Federation v2.0 official documentation](https://module-federation.io/) for detailed usage.

### Module Federation v1.5

This is the version built into Rspack. In addition to supporting Module Federation v1.0's capabilities such as module export, module loading, and dependency sharing, it also adds runtime plugin functionality, allowing users to extend the behavior and functionality of module federation.

You can use it through Rsbuild's [moduleFederation.options](/config/module-federation/options), no need to install any plugins.

```ts title="rsbuild.config.ts"
export default defineConfig({
  moduleFederation: {
    options: {
      name: 'remote',
      // other options
    },
  },
});
```

## Example Repositories

Rsbuild has provided some example projects of Module Federation, you can refer to:

- [Module Federation v2.0 Example](https://github.com/rspack-contrib/rspack-examples/tree/main/rsbuild/module-federation-enhanced)
- [Module Federation v1.5 Example](https://github.com/rspack-contrib/rspack-examples/tree/main/rsbuild/module-federation)
